Thread grinding machine



y 1945- H. v. CHRISTENSEN 2,375,079

THREAD GRINDING MACHINE Filed Feb. 22, 1943 9 Sheets-Sheet l INVENTOR E .1. //d/v/4 en$e/z Cy ATTORNEFS- y 1945- H. v. CHRISTENSEN 2,375,079

THREAD GRINDING MACHINE Filed Feb. 22, 1943 9 Sheets-Sheet 2 /0 INVENTOR E Harv Z1 czrwzemfem BY W VX214 ATTORNEYS y 1945- H. v. CHRISTENSEN 2,375,079

THREAD GRINDING MACHINE Filed Feb. 22, 1943 9 Sheets-Sheet 5 IN VENTOR HardZa f'firzaz 'ezzsen.

ATTORNEYS.

i 1945- H. v. CHRISTENSEN 2,375,079

THREAD GRINDING MACHINE 9 Sheets-Sheet 4 Filed Feb. 22, 1945 INVENTOR BY W MQ ATTORNEY5.

M y 1945- H. v. cHRlsT NsEfi 2,375,079

T READ GRINDING MACHINE F'ilpd Feb. 22, 1943 9 Sheets-Sheet 5 IN VE N TOR ATTORNEYS.-

y 1, 1945- H. v. CHRISTENSEN 2,375,079

' THREAD GRINDING MACHINE Filed Feb. 22, 1943 A 9 Sheets-Sheet 6 /e'7 J I J /76 A 55 54 I 26 J /7 Z I Q) I J q/go 'l 2 i E i INVENTOR A TTORNE y 1945' H. v. CHRISTENSEN 2,375,079

THREAD GRINDING MACHINE Filed Feb. 22, 1945 9 sheets sheet 7 6 ATTORNEY5.

y 1945- H. v. CHRISTENSEN 2,375,079

THREAD GRINDING MACHINE Filed Feb. 22, 1943 9 Sheets-Sheet 8 IN VE N TOR f/a rvZJ fifz'lfz eflsen ATTORNEY y 1945- H. v. CHRISTENSEN 2,375,079

THREAD GRINDING MACHINE Filed Feb; 22 1945 9 Sheets-Sheet 9 i ll //0 y III 7" f g r map/a2:

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INVENTOR E fid/dZJ 6%rzlgferzsez2 ATTORNEYS.

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Patented May 1, 1945 THREAD GRINDING MACHINE Harold V. Christensen, St. Clair Shores, Mich., as-

signor to Michigan Tool Company, Detroit, Mich, a corporation of Delaware Application February 22, 1943, Serial No. 476,729

7 Claims.

The present invention relates to apparatus for polishing worms for use in worm gearing, and particularly relates to improvements in the apparatus disclosed in the co-pending application of George R. Scott, Serial No. 417,647, filed November 3, 1941, and which is now Patent No. 2,337,776. 1

One of the primary objectsof the present invention is to provide improvements in machines of the type mentioned in which worms may be polished in an improved manner, particularly in which the thread form may be more accurately and quickly polished than in prior machines.

Another object of the invention is to provide improvements in machines of the type mentioned, in which the polishing belt is so mounted as to be positioned adjacent the work for accurately polishing worms of different helix angles.

A further object of the invention is to provide an adjustable guide for thebelt in machines of the type mentioned, in which the guide is so positioned adjacent the work that the entering and leaving positions of the belt may be varied for worms of different helix angles.

Another object, of the invention is to provide improvements in belt mountings of the type mentioned, so that the belt may be quickly released Another object of the invention is to provide improvements in the operating mechanism of machines of the type mentioned for accomplishing an oscillating action of the work element.

Another object of the invention is to provide improvements in machines of the type mentioned, so that the belt is mounted and caused to follow the contour of the worm thread, and particularly to follow the contour of threads having end relief as shown in Scott Patent No. 2,279,414, issued April 14, 1942.

Other objects of the invention will become apparent from the following specification, the drawings relating thereto and from the claims hereinafter set forth.

In the drawings, in which like numerals are used to designate like parts in the several views throughout:

Figure 1 is a front elevational view of a polishing machine embodying features of the present invention;

Figure 2 is a side elevational view of the machine shown in Figure l, and taken from the right side of Figure 1;

Figure 3 is a top plan view of the machine shown in Figure 1;

Figure 4 is a partial side elevational view of the machine, and taken from the left side of Figure 1;

Figure 5 is a front elevational view of the work head and showing the manner in which the belt is mounted on such head;

Figure 6 is a side elevational view of the structure shown in Figure 5 and taken from the left side of Figure 5;

Figure 7 i an elevational view of the guide mechanism taken substantially along the line '|--l of Figure 6;

Figure 8 is a top plan view of the work table;

Figure 9 is a side elevational view of a portion of the structure shown in Figure 8, and taken in the direction of the arrow 9, of Figure 8;

Figure 10 is a cross-sectional view taken substantially along the line Ill-10 of Figure 8;

' Figure 11 is a fragmentary, vertical, cross-sectional view showing the mounting and drive structure for the table shown in Figure 7;

Figure 12 is a partial end elevational view taken in the direction of the arrow [2 of Figure 8 and leaving out one of the end relief controls for purpose of clarity;

Figure 13 is a cross-sectional view taken substantially along the line |3l3 of Figure 12, and showing the end relief control omitted from the view of Figure 12;

Figure 14 is a diagrammatic view of the driving mechanism of the machine of the present invention; and

Figure 15 is a diagrammatic view of the electric control panel employed in the present invention.

In general, in the machine of the present invention, a worm ear of the type disclosed in Scott Patent No. 2,279,414, with or without the end relief there claimed, is ground or polished by means of an abrading element which is caused to engage the side of the thread of the worm. The worm is mounted on a horizontal spindle and the grinding or polishing element, which in the embodiment illustrated is in the form of an endless abrading belt, is mounted upon a vertical spindle. The belt is urged into engagement with the side of the thread and is caused to oscillate in synchronism with the reversed rotation of the worm spindle so that that portion of the belt which engages the worm follows the contour of the worm thread from one end to the other and return, repeating this until the thread is properly ground. 2

Referring to the drawings, the machine comprises a base Ill having an upstanding standard l2 disposed at the back thereof. Such back portion l2 has a vertical face It formed with a horizontal guideway I6 which is adapted to have slidably mounted thereon a head stock I8 and a tail stock 20. The head stock It has the drive spindle 2| disposed therein for driving a worm 22 to be ground. The head and tail stock It and 20 are slidable within the guideway I6 for the purpose of properly positioning them and may be fixed in place upon the guideway I6 in the usual way.

IA supporting standard 24 is mounted on the base I and is slidably supported on horizontal guideways 26 which are disposed at a right angle to the axis of the worm 22. The standard 24 is slidable on such guideways and is connected to the base I0 through a conventional screw and nut connection having a hand wheel 28 associated with the screw for the purpose of adjustably positioning the standard 24 with respect to the axis of the worm so that it may be set at the proper center distance with respect thereto.

Grinding or polishing means generally indicated at 30 is mounted on the support 24 for oscillation with respect thereto and for bodily movement therewith so that it may be disposed on the proper center distance with respect to the worm.

The grinding or polishing means 30 is mounted upon a top table 32 (Figures 1, 5, 8 and 11) through interconnecting means which permit adjustment in two directions, at right angles to each other, so that the grinding means may be properly positioned with respect to the worm thread. Such means 30 includes a base 34 which is interconnected to a member 36 through guideways 38. A screw and nut interconnection i provided between the member 34 and the member 36 for the purpose of slidably adjusting the member 34 with respect to the member 36 along guideways 38. The screw has a square head, indicated at 50, which may be engaged by a suitable tool to provide the adjustment, and Vernier scales are provided to indicate the position of the adjustment. A suitable locking means may be provided to lock the member 34 in it adjusted position with respect to the member 36.

The member 36 is connected to the member 32 by means of parallel guideways 42, which are disposed at a right angle to the guideways 38. The member 36 is interconnected to the member 32 by means of a conventional nut and screw having a hand wheel 44 connected to the outer end of the screw for the purpose of slidably adjusting the member 36 with respect to the member 32. Locking means may be provided for locking the member 36 in its adjusted position with respect to the member 32. Thus, the base 34 may be adjusted with respect to the member 32 by moving it in the directions of the guideways 38 and 42.

The base 34 includes anupstanding portion 46, which terminates in an upwardly opening, cupshaped cylindrical recess 48. The recess 38 receives therein a vertical tubular post 50.

A tubular sleeve 52 having its upper end closed by means of a plate 54 is telescopically received over the upper end of the tubular member 50. A compression coil spring 56 is disposed within the tubular member 50, and the lower end of such spring rests upon the base of the recess 48 with the upper end bearing against the underside of plate 54 of the sleeve 52. This is to provide a resilient mounting for the sleeve member 52.

The sleeve member 52 may be adjustably positioned against the action of the spring 55, with respect to the tubular'rnember 50, by means of a rack and gear connection, rack teeth 58 being formed in the peripheral surface of the tubular I thereto by means of suitable screws I04.

member 50 adjacent the upper end thereof. A hand wheel 60 is mounted to the member 52 transversely of the axis thereof and is connected to a shaft having a gear 62 keyed thereto which is adapted to mesh with the rack teeth 58. Thus, by turning the hand wheel 60, the member 52 may be adjusted with respect to the member 50. The member 52 may then be locked in place by a conventional lockscrew.

The member 52 has an integral bracket 64 formed adjacent the upper end thereof which serves to pivotally mount one end of a base plate 56 by means of pivot pins 68. A drive motor 10 is fixedly mounted to the top surface of the plate The end of the plate 66, opposite to that of the pivot 68, is connected to the member 52 by means of a toggle linkage including an L-shaped linkage member I2 which is pivotally connected to the member 66 by means of a pivot pin J4. The linkage member 12 is pivotally connected to the other link I6 of the toggle linkage by means of pivots I8. The link 16 is adjustable in length and is formed in two interengaging parts which are longitudinally movable with respect to each other for the purpose of adjusting the length of the link 16. One of such members may be in the form of a threaded screw which is received within a bore in the other member and a nut may be provided for adjusting the length of the link. The lower end of the link is pivotally connected to the member 52 by means of a pivot pin 82. The purpose of the toggle link is to permit a quick downward pivoting of the base 66 about pivot 68 when the link 72 is broken so that the polishing belt may be quickly changed.

Tension springs 86 are disposed on opposite sides of the plate member 66 and have their upper ends connected to the plate member 66 and their lower ends connected to the sleeve member 52 The tension springs 86 serve to constantly urge the plate member in a clockwise direction (viewing Fig. 5) about pivots 68 so that when the toggle I2 is in the locked position shown in Fig. 5, it is held locked until manually released. The toggle is thus broken only by manual pressure against the action of springs 86.

A pulley 88 is keyed to the end of the motor shaft of motor 70 and is adapted to have an endless abrading belt 90 trained thereabout. The lower end of the abrading belt 90 is trained about a pulley 92. The pulley 92 is fixed to a shaft 94 and such shaft is rotatably mounted Within suitable bearings mounted in the lower end of depending bearing bracket 96. The bearing bracket 96 has a split collar 98 provided with a tightening bolt 99, and such bracket is mounted to the standard 46.

The split sleeve 98 member IOI having a I0! is mounted to the is received over a tubular flange I02. The member standard 46 and secured The member 46 has a horizontal bore I06 therethrough, and the bore I08 through the tubular member IOI is axially aligned with the bore I06. The split collar 98 may be received over the member If and secured thereto in its proper position by tightening the bolt 99.

A cylindrical member I I0 bores I08 and I06, and such vided with an axial recess is pressed into the member H0 is proin one end thereof which is adapted to removably receive the base of a cylindrical, pencil spindle II2. Such spindle I I2 is removably disposed within the member I I0, and may be secured therein by means of a set screw or the like. The outer end of the member H2 is of a reduced and, small diameter and is adapted to engage ,the inside of the abrading belt 30 so that the outer side of the belt, which carries the abrasive, is urged against the surface of the thread of the workpiece. The outer end of the pencil spindle I I2 i of such a small diameter that it may readily extend between the threads of the worm and the reduced portion is of substantially the same length as the width of the belt. The width of the belt is substantially the same as the face depth of the worm thread.

In order to properly guide the entering and leaving portions of the belt, which will be caused to engage the worm thread in line contact by the pencil spindle, guide rollers are provided, a best shown in Figures 6 and '7. Such guide rollers include a pair of rollers II4 on one side of the spindle I I2 and another pair of rollers II6 on the opposite side of the spindle H2. The pairs of rollers are mounted upon a mounting member having a hub portion I I8 with outwardly extending ears I20 and I22. The rollers II4 are rotatably mounted on ear I20, and the rollers II6 are rotatably mounted on ear I22. The hub portion I I is split and is disposed over the outer end of tubular member IN. The ears I and I22 are offset from a diameter with respect to each other, and the belt 90 passes between the rollers and about the spindle II2 so that the entering and leaving portions of the belt are at an angle with respect to each other. Such angle, in the embodiment illustrated, is approximately ten degrees and provides for clearance of the belt as it is urged into engagement with the worm thread so that the engagement of the belt with the worm is practically line contact.

The outer edge of member IOI is provided with a scale and it will be seen that the hub portion lit may be rotated about member IOI and held in its adjusted position by means of a bolt I24, so that the belt may be adjusted to approach and leave the engaged portion of the worm thread at different angles. The guide roll H4 and H6 are thus bodily adjusted about the spindle H2. The purpose of this is to accommodate the machine to worms of different helix angles.

As disclosed in the Scott patent, No. 2,279,414 above referred to, worms of the type for which the present machine is particularly useful are employed in the Conetype ofdouble enveloping worm gearing. The flanks of the thread of the worm are sinuously warped surfaces, which surfaces are generated by a straight line element. This straight line element lies in a plane, passing through the axis of the worm and perpendicular to the axis of the wheel with which the worm is adapted to mesh. The intersections of these tooth flanks with this plane all he along straight lines which are tangent to a .circle whose center coincides with the axis of the wheel with which the worm is adapted to mesh.

In the present machine, the polishing or grinding means is so positioned on the supporting table that the periphery of the spindle I I2 on the entering side adjacent the side of the thread being worked upon is disposed on a tangent to the base circle of the worm gear or wheel with which the worm workpiece is adapted to mesh. The 1ongitudinal axis of the spindle H2 is horizontally positioned so that it i in the mid-plane or axial plane of the workpiece as it moves across the worm. The thickness of the belt 30 is exaggerated in the drawings shown, and, in fact, it i quite thin so that the belt will engage the workpiece along the line mentioned above. I

As mentioned above, the grinding or polishing means 30 i mounted upon the top table 32. Such top table 32 is in turn mounted upon and interconnected to a main table I 26. The tables 32 and I26 are interconnected together so that they are driven together, but relative movement is permitted between such tables in a manner that will be described in detail hereinafter.

The table I26 is rotatably mounted upon the standard 24, as best shOWn in Figure 11, and the table I26 is connected to and adapted to be driven by a vertical drive spindle I28, which is mounted within suitable bearings I30 within a vertical bore in standard portion 24. The table I26 i fixedly connected to the spindle I28 by means of bolts I32. The table 32 is supported on the top surface of table I26 by means of roller bearings I34, and a resilient driving connection is provided between tables 32 and I26 so that such tables are driven together.

Such resilient driving connection is best shown in Figures 12 and 13, and includes depending cylindrical members I38 which are formed integral with the undersurface of the overhanging portion of table 32. The cylindrical members have axially aligned bores I40 formed therein and each of such bores is adapted to receive therein a compression coil sprirlg I42. A screw plug I44 is disposed in one end of each of the members I38, and bears against one end of the compression spring I42. The opposite end of each compression spring is received within a cup-shaped member I46, which is slidably disposed within the bore I40 and which has a semi-spherical knob I48 formed on the outer end thereof An outwardly projecting arm I50 is secured to the peripheral edge of table I26 by means of bolts I52, and such member I50 extends between the facing portions of members I36. Bearing surfaces I54 are formed on the member I50, and such bearing surfaces are adapted to have the projections I48 resiliently bear thereagainst. The opposite springs I42, in bearing against the member I50, provide the drive connection between tables 32 and I26, in either direction of drive of such tables. Such resilient means, however, permits limited relative movement between such tables.

The relative movement between the tables is provided so that the abrading member follows the contour of the worm thread when such worm thread is provided with the gradual end relief disclosed and claimed in Scott 2,279,414, above referred to.

In the operation of the machine, the tables I26. and 32 are caused to oscillate with respect to the worm and the abrading belt engages the worm during such oscillation. Th abrading means is rotated in one direction and the worm is rotated in one direction. The direction of rotation of both is then reversed so that the pencil spindle H2, in its engag'ement against the belt 90, passes from oneend of the thread to the other end, then the direction of the pencilspindle and the worm are reversed, so that the pencil spindle returns to its first position while the worm is reversely turned.

The drivin means for the spindles will be described hereinafter. Such driving means also includes a side feed means so that the grinding means, including the pencil spindle, are fedtoward the side of the thread in order to remove the desired amount of material from the work- Patent No.

of-the-way position, but it will piece. Such side feed described hereinafter.

As the grinding belt engages the worm thread adjacent the ends of the thread, and when the worm is of the type having the end relief above referred to, means are provided to move the tables 32 and I26 relative to each other so that the pencil spindle urges the belt into engagement with the worm thread over those portions at the ends which have been gradually relieved as well as in the normal, central portion. Such means includes a bell crank member I60 which is fulcrumed to the outer end of member I50 by means of a pivot pin I62. One arm of the bell crank member I60 projects radially outwardly and has a pivot pin I 64 connected thereto on which a square member I66 is mounted. The is received within a rectangular groove I60 of a member I61 whichis secured within a groove in the undersurface of the overhanging end of table 32.

It will be appreciated that, as the bell crank I 60 is rocked about its pivot I66 will correspondingly rock about the pivot I64 and slide within slot I66 to cause a relative mechanism will also be movement between tables I26 and 32 against the action of the resilient springs I 62.

In order to accurately control the degree of such relative movement, the other arm of the bell crank member I60 has a roller follower I connected to the outer end thereof and depended therefrom. Such roller follower I10 is adapted to engage the cam surfaces of cam plates I12 as the tables 32 and I26 approach either end of their oscillation. The cam plates I12 have cam edges of proper contour, depending upon the contour of the end relief on the worm, and are adjustably supported on the standard portion 24 and may be set to give the desired contour and extent of end relief or may be positioned inwardly where they are out of the path of movement of the roller follower I10 when no end relief is present on the workpiece. In the drawings, the cams I12 are illustrated in such outbe readily apparent that they may be positioned so as to be engaged by the cam follower.

The mounting for the cam members I12 includes a base plate I14 which may be suitably positioned within a slot I16 formed on the periphery of standard portion 24. The plates I14 may be fixed in position in such slot by means of nuts and bolts I18.

Each member I16 is formed with a transverse uide slot I80 in the top surface thereof which slidably receives therein a mounting plate I82 having an undersuri'ace complementary in shape through member I12, for the purpose of fixing the member I82 in its proper position within slot I66. The member I12 is fixed to the upwardly projecting end of tubular member I86 for rotation therewith, and such member I06 is formed with gear teeth I90 on the peripheral surface thereof.

I62, the member' the cam plates I12 may be adjusted to the proper position-for the desired end relief contour.

With the members I12 positioned for the desired end relief, it will be appreciated that, when the roller follower I10 engages either of the cam members, the bell crank I60 is caused to rock to provide the relative movement between tables 32 and I26 which causes the spindle II2 to follow the thread form throughout its length.

The spindle 2I, to which the workpiece 22 is attached, and the vertical spindle I28, to which the grinding means 30 is connected, are driven insynchronism. The spindle 2| is connected to a drive shaft 200; and the spindle 28 is connected through a Wormgear 202 and worm 204 with a drive shaft 201. A main drive motor I, which is a variable speed, reversible motor, is mounted on the standard I2 and has an outwardly extending shaft 201 associated therewith. A hand wheel 206 is connected to the outer end thereof for varying the speed of the drive.

The drive motor I50 is connected to the shaft 200 through change gears 2I0, 2I2, 2M and 2I6, the gear 2I6 being keyed to shaft 200. The shaft 206 i driven through the same change gears and in addition through change and reduction gears 2I8, 220, 224, 226, 228, 230 and 232. is keyed to a shaft shaft 206.

The shafts 234 and 206 are interconnected through a matching differential generally indicated at 236. Such matching differential 236 may be of the same structure as the matching differential employed in the machine of Pelphrey application, Serial No. 435,649, filed March 21, 1942. The matching differential 236 is employed for the purpose of providing the relative side feed of the vertical spindle with respect to the hori- 234 which is aligned with from the worm.

The matching differential includes a cylindrical housing or rotatable drum 240, into which the aligned shafts 234 and 206 extend. The housing 240 is mounted for rotation within suitable bear- 1 ings on the standard I0 and may be revolved about the axis of shafts 234 and 206. A gear 242 is keyed to the inner end of shaft 206 and another gear 244 is keyed to the inner end of shaft 234. An idler gear. 246 is mounted within the housing 240 on a shaft which is mounted on suitable bearings therein, and such gear meshes with gears 244 F and 242. The gear 246 is free to rotate about its own axis but revolves about the axis of gears 242 and 244 when the housing 240 is revolved. The gears 242 and 244 have the same outside diameter but gear 242 ha less teeth than gear 244. For example, gear 244 may have twenty-four teeth, gear 246 have thirteen teeth and gear 242 twenty-three teeth. The gear center dstances for the gears 242 and 244 with respect to gear 246 are the same. The twenty-four tooth gear may be made standard, While the twenty-three tooth gear is cut to mate with the thirteen tooth gear. All geometrical laws of the involute curve are strictly observed in the formation of these gear teeth.

The construction of the matching differential 236 thus provides a great gear reduction within itself for the side feed mechanism, as one turn of the housing or drum 240 rotates gear 242 one twenty-third of a revolution. Thus, it is possible through this means to accomplish the relatively Gear 232 drive in a very accurate manner.

This side feed is accomplished by rotating the.

housing 240, and such housing is formed with a ring of worm gear teeth 248 therearound which mesh with a worm 250.

The drum is rotated by means of the side feed motor I52 which'is connected to a drive shaft 252, to which the worm 250 is keyed. The motor I52 may be connected to the shaft 252 through gear reduction worm and gear sets 254 and 256.

A hand operated jaw clutch 258 is inserted between sections of the shaft 252 so that the drive shaft 252 may be thrown out of drive by the motor H2 and a side feed hand wheel 260, which is connected to the forwardly projecting end of shaft 252, may be hand operated to side feed by hand.

The sidefeed is either to right or left, depending upon which side of the worm thread is bein worked upon. In the embodiment illustrated the grinding means is set to operate on the right side of the worm thread, Viewing Figure 1, so that the side feed would be to the left. When the opposite side of the thread is to be worked upon the opposite reach'of the belt 90 is engaged by the guide rollers with the guide rollers rotated through substantially 180 from the position shown. The table is also set so that the spindle is tangent to the base circle above referred to.

As mentioned above, the spindle I28 is caused to oscillate and the spindle 2I is correspondingly reversed in its direction of rotation. The variable speed motor I50 is reversible and control means are provided for reversing the direction of motor I56. Such means include a limit switch indicated at LSI, which is disposed adjacent the pc- -from main supply line I54.

motor I50 and ide feed motor I52 are diagrammatically illustrated in their relation to the electric control panel. The drive motor I50 and the side feed motor I52 receive their current A drum switch I66 is interposed in the main line adjacent the reed motor I52 and, when in the position shown, the feed is to the right. With the switch I56 positioned oppositely from that shown, the feed would be to the left. The current from'the main line 3 is supplied to the control panel through a transformer indicated at I58.

In the setting up operation, it may be desirable to disconnect the feed mechanism by disengaging the clutch 268 and positioning the work by the hand wheel 260. If this is done, LS5 is opened by the clutchlever and the only operation that can now be performed is by the jog button. It will be seen from the diagram that when the jog button is'depressed, the upper section thereof closes gap I60 and opens the lower gap I62 so riphery of table 126. Actuating arms 260 and 262 are secured to the table I26 within a T-slot 264 provided in the periphery thereof. Such members 262 may be suitably adjusted within such slots so as to effect the reversal at the proper time. The limit switch LSI has an actuating arm 266 projecting upwardly therefrom in the path of move-- ment of the reversing arms 2.60 and 262. Thus, when the table I26 is rotating in one direction one of the arms 260 or 262 strikes the actuating arm 266 of LSI causing the motor I50 to reverse, In

the reverse direction the other stop arm engages the actuating member 266 to cause another reversal.

Control means are also provided for controlling the extent of side feed and such control means includes limit switches LS2, LS3, and LS4, which have actuating arms disposed to be actuated'by a traveling nut 210. The traveling nut 210 is mounted on a screw 212 which is operatively connected to the side feed motor I52 through a worm and gear set 214 and sets 254 and 256. As the screw 212 is caused to turn nut 210 is moved along the screw 212 in a'direction depending upon the direction of rotation of motor I52. When in one position, the central position LS4 is actuated and when in positions to the right 'or left, LS2 or LS3 are actuated through engagement of the nut with the stops 218 or 280 which are adjustably mounted on rod.282. Engagement of either or these stops causes shifting of rod 282 which causes actuation of either LS2 or LS3 through depending fingers 284 which en-,

ease the actuating arms of the limit switches.

In order to automatically control the operation of the present machine an electric control panel is diagrammatically illustrated in Figure 15.

Referring to Figure 15, the variablespeed drive by the motor I52, the v that current is supplied coils and relays F and R as LSI is actuated. I

In the normal operation of the machine, the clutch 258 is engaged and LS5 is closed, as shown. Pressing of the start button energizes counter or timer clutch coil T through LS5 and such coil T establishes its own holding circuit through normally open contact Ta which closes when T is energized. At this stage in the operation, contact "TRIa. is in the position shown with the upper contact closing gap I64 and withthe lower contact open acrom gap I66. With LSI in the position shown, coil or relay F is energized across gap I64 through TRIa, LSI and normally closed contact Ra.

When coil F is energized, normally closed contact Fa is opened and normally open contacts F1), F0, Fd, Fe, and Ff are closed. With Fd, Fe, and 1? closed, the drive motor I60 turns in the forward direction until LSI is actuated by one of the stops 260 or 262 on the table I26 to open gap I68 and close gap I10. When gap I68 is opened,coil F is de-energized and Fa returns to its normally closed position so that coil R is energized across closed gap I10. When coil R is energized, normally closed contact Ra is opened 7 and normally open contacts Rb, R0, Rd, Re, and

Rf are closed. Contacts Fb, Fc, Fa, Fe, and F open and drive motor I50 is reversed to drive the table in the reverse direction until LSI is again actuated to tie-energize coil R and energize coil F. When coil F is tie-energized and coil R energized, the circuit to TRI is maintained through Ric.

When TRI is energized, TRIa moves from the position shown upwardly to open gap I64 and close gap I66; however, coils F or R are maintained energized through contacts Fe or Rb, depending upon the position of LSI.

When TRI is initially energized, the top and.

bottom portions of the contacts TRIa act instantly to open gap I64 and close gap I66.

The timer, including the coil TRI and the contacts mm, is so constructed that upon energize.- tion of coil TRI the upward movement oi TRIa is instantaneous to close gap I66 and open gap I64; but when TRI is tie-energized the downward movement of TRIa. is pneumatically timed so that there is a predetermined lag between the de-energizing of TRI and the closing oi. gap I64 and opening of gap I66. This permits a time interval between the forward and reverse movemcntoi the table or the energization of coils F and R so that there is not a sudden stop and reversal in the machine parts.

There is an auxiliary ccntactor TRI b on the timer TRI in series with the feed circuit which opens upon energization of coil TRl preventing the energization of the feed coil FD during the time that RRl is energized.

When L8! is actuated, F or R is de-energized, depending upon the position of LS! which in turn de-energizes 'I'Rl; and at this instant TRlb returns to closed position while'the upper portion of TRla across gap ltd is timed out, thereby completing the circuit to feed coil FD. With FD energized, FDc, FDcZ, and FDe are closed causing the feed motor l 52 to run to obtain the feed until TR2 times out. Coil TRZ is energized through FDa, which is closed when FD is energized. The timer, including coil TR2 and contact TRia, is

such that when coil TR2 is energized, TRZa remains in the closed position shown for a timed interval at which time TRZa, opens to de-energize FD. When FD is de-energized, the motor I52 stops when contacts FDc, FDa, and FDe open. Motor I52 is provided with a three-phase brake so that when the motor contacts are opened the motor is instantly braked to stop the feed.

It will thus be seen that the feed coil FD is energized at the end of each of the forward and reverse movements of the table or at each time that the reversal of motor 852 takes place. Also,

from the above, it will be understood that there is a time period before the energization of coils F or R, such time period being controlled by the normally closed portion of I'Rla across gap I66 which falls back to such normally closed position in accordance with the setting of the pneumatic timer mentioned above, to energize F and R.

The above action in the alternate energizing of coils F and R takes place and the incremental feed due to the energizing of coil FD takesplace until the traveling nut 21d, associated with the feed, has progressed to a point of actuating either LS2 or LS3, depending upon the position of the drum switch I56. With the drum switch in the position shown, the feed is to the right, viewing Figure 14, so that the above action would not take place until LS2 was actuated. LS l is held open when the traveling feed nut 210 is in the central position shown in Figure 14, but as soon as the nut moves away from its central position, which may occur after the first, or one of the first several, impulses of FD, LS l closes and remains closed until the traveling nut returns to its central position and again engages LS l to open it. At the initial stage of the operation, counter or timer clutch coil T is energized to close normally open contacts Ta and Tb so that the holding circult for FR, FD, IE2, and TR! is maintained through Ta when the start button is released. When Th2 is closed, coil GR! is energized so that it establishes its own holding circuit through CRla and through LS4 when it is closed. When coil T is energized, normally closed contact Tc opens so that coil RT cannot be energized.

When LS2 is engaged, gap I'l2 is closed and gap I'M is opened. With gap 1 3' open, coil FD cannot be energized so that the feed is no longer operated at the reversals of F and R; but instead an actuating or impulse coil A is energized a preset number of times. At the last count of the preset number of times, the counter or timer clutch associated with coil T is mechanically opened so that coil T is tie-energized thereby opening the entire control circuit above this point.

Before this takes place, that is, before the preset number of impulses to counter coil A takes place, there is no feed, but the alternate energizing of coils F and R continues so that the polishing band 9!] continues to engage the work for a final finishing operation. That ls, the polishing belt will continue to pass through the worm in engagement with the side of the thread for a preset number of times without side feed.

After counter coil A counts out and coil T is de-energized, the remainder of the cycle is devoted to returning the traveling nut to its center position. To will then return to its normally closed position and coil RT will be energized through normally closed contacts FDb, CRla and closed LS4 and LS5. When the traveling nut reaches its central position, LS4 is opened so that coil RT is de-energized.

Going back to the beginning of the cycle, LS4 was initially held open by the normal, center position of the traveling nut. However, it is closed by spring action when the nut travels away from its central position. Nothing happens in this part of the circuit until the counter counts out normally closing contact Tb which energizes CRI which sets up its own holding circuit through CRIa. When coil RT is energized through CRIa, contacts RTc, RTd, and. RTe are closed to run the feed motor in the reverse direction until LS4 is opened by the travelin nut which instantaneously stops the feed motor through the three-phase brake. This terminates the normal cycle.

By the position of the drum switch, the above cycle of operation can be either to the right or to the left, which enables finishing the worm on either side of the worm thread. The above description has been with the feed to the right, but if the drum switch I56 were oppositely positioned, the feed would be to the left. Otherwise,=v the operation would be the same as that described above.

The log button is provided for operating coils F and R only. The return button is provided in case the stop button should be depressed while on the return and so that the return only can be continued. That is, it will be seen that when the return button is actuated the gap H6 is opened and gap I18 closed. With gap H8 closed. RT and CR! would be energized while all of the circuit above gap I16 would be open.

Normally closed contact RTa is provided in series with coil FD and normally closed contact FDb is provided in series with coil RT so that there can be no actuation of the return during feed nor can there be an actuation of the feed during return.

From the above description of the automatic cycle it will be understood that the normally open contacts are illustrated by the spaced parallel lines, and the normally closed contacts are illustrated by the spaced parallel lines having a cross line passing through the parallel lines. Energization of the various coils closes their respective normally open contacts and opens their respective normally closed contacts, such contacts being connected to their coils in the usual way. The contacts for the various coils or relays are indicated by sub-letters. The elements employed in the electric control circuit are conventional elements obtainable on the market and their structures are understood by those skilled in the art.

What is claimed is:

1. Apparatus for polishing the thread sides of an area contact type of worm comprising a spindle for rotatably mounting a worm, a supporting table mounted for movement about an axis coinciding with the axis of rotation of a worm wheel with which said worm is adapted to mesh, an endlessv polishing belt carried on said. supporting table, said belt having a width generally the same as the depth of the thread of the worm being polished, means operatively connected to said belt for driving said belt, means mounted on said table adjacent said "belt for engaging the inside of the belt and for urging the opposite side of said belt into engagement with the side of worm thread, and guide means mounted on said table and disposed on opposite sides of said last named means in engagement with the belt on the side opposite to that engaged by said last named means to control the entering and leaving positions of the belt with respect to said last named means 2. Apparatus for polishing the thread sides of an area contact type of worm comprising a spindle for rotatably mounting a worm, a supporting table mounted for movement about an axis coinciding with the axis of rotation of a worm wheel with which said worm is adapted to mesh, an endless polishing belt carried on said supporting table, said belt having a width generally the same as the depth of the thread of the worm being polished, means operativelyconnected to said belt for driving said belt, means mounted on said table including a pencil spindle engaging the inside surface of said belt for urging said belt into engagement with the side of worm thread, guide means disposed on opposite sides of said pencil spindle in engagement with the belt on the side opposite to that engaged by said pencil spindle to control the entering and leaving positions of the belt adjacent said of the worm being polished, means operatively connected to said belt for driving said belt, means mounted on said table including a pencil spindle engaging the inside surface of said belt for urging said belt into-engagement with the side of worm thread, guide means including rollers disposed, on opposite sides of said pencil spindle in engagement with the belt on the side opposite to that engaged by the pencil spindle to control the entering and leaving positions of the belt adjacent said pencil spindle, said rollers being so positioned with respect to each other and to said pencil spindle that the belt portions on opposite sides of said pencil spindle are at an angle with respect to each other, and means mounting said rollers for bodily adjustment about the center of said pencil spindle so as to vary the entering and leaving positions of the belt with respect to the work adjacent said pencil spindle.

5. Apparatus for polishing the thread sides of an area contact type of worm comprising a pencil spindle, and means mounting said guide means for bodily adjustment about the center of said pencil spindle so as to vary the entering and leaving positions of the belt with respect to the work adjacent said pencil spindle.

3. Apparatus for polishing the thread sides of an area contact type of worm comprising a spindle for rotatably mounting a worm, a supporting table mounted for movement about an axis coinciding with the axis of rotation of a worm wheel with which said worm is adapted to mesh, an endless polishing belt carried on said supporting table, said belt having a width generally the same as the depth of the thread of the worm being polished, means operatively connected to said belt for driving said belt, means mounted on said table including a pencil spindle engaging the inside surface of said belt for urging said belt into engagement with the side of worm thread, and guide means mounted on said table including rollers disposed on opposite sides of said pencil spindle in engagement with opposite sides of the belt on the side opposite to that engaged by said pencil spindle to control the entering and leaving positions of the belt adjacent said last named means, said rollers being so positioned with respect to each other and to said pencil spindle that the belt portions on opposite sides of said pencil spindle are at an angle with respect to each other.

4. Apparatus for polishing the thread sides of an area contact type of worm comprising a spindle for rotatably mounting a worm, a supporting table mounted for movement about an axis coinciding with the axis of rotation of a worm wheel with which said worm is adapted to mesh, an endless polishing belt carried on said supporting table, said belt having a width generally the same as the depth of the thread spindle for rotatably mounting a worm, a supporting table mounted for movement about an axis coinciding with the axis of rotation of a worm wheel with which said worm is adapted to mesh, an endless polishing belt carried on said supporting table, said belt having a width generally the same as the depth of the thread of the worm being polished, means -operatively connected to said belt for driving said belt, means mounted on said table including a pencil spindle engaging the inside surface of said belt for urging said belt into engagement with the side of worm thread, guide means including rollers disposed on opposite sides of said pencil spindle in engagement with the belt on the side opposite to that engaged by said pencil spindle to control the entering and leaving positions of the belt adjacent said pencil spindle, said rollers being so positioned with respect to each other and to said pencil spindle that the belt portions on opposite sides of said pencil spindle are at an angle with respect to each other, and means mounting said rollers for bodily rotation about the center of said pencil spindle through substantially so that when in one position the rollers engage one reach of the belt and when in the other position engage the other reach of the belt.

6. Apparatus for polishing the thread sides oi an area contact type of worm comprising a rotatable spindle for rotatably mounting a worm, another spindle having a supporting table mounted thereon for rotative movement about an axis coinciding with the axis of rotation of a worm wheel with which said worm is adapted to mesh, means iorrotating said spindles about their respectives axes in synchronism first in one direction and then in the opposite direction, a belt,

supporting member mounted on said table for limited relative rotative movement with respect thereto, resilient means interconnecting said supporting member and table to resiliently urge said supporting member to a normal position with respect to said table, means connectible with said supporting member and responsive to movement of said supporting member for causing such relative movement by moving said supporting member out of its normal position, an endless polishing belt carried on said supporting member, means operatively connected to said belt for driving said belt, and means engaging the inside surface of said belt for urging said belt into engagement with the side of the worm thread.

7. Apparatus for polishing the thread sides of an area contact type of worm comprising a rotatable spindle for rotatably mounting a worm, another spindle having a supporting table mounted thereon for rotative movement about an axis coinciding with the axis of rotation of a worm wheel with which said worm is adapted to mesh, means for rotating said spindles about their respective axes in synchronism first in one direction and then in the opposite direction, a beltsupporting member mounted on said table for asmove means. engaging the inside surface of said belt for urging said belt into side of the worm thread.

HAROLD V. CHRISTENSEN.

engagement with the 

